View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by Directory of Open Access Journals Functional Foods in Heals and Disease: 2:61-74 Page 61 of 74 Risearch Open Access Bio-active compounds of bitter melon genotypes (Momordica charantia L.) in relation to their physiological functions Shahidul Islam1, Mohammad Jalaluddin1, and Navam S. Hettiarachchy2 1Department of Agriculture, Mail Slot 4913, University of Arkansas at Pine Bluff, 1200 North University Drive, Pine Bluff, AR 71601, USA; 2Department of Food Science, University of Arkansas, Fayetteville, AR 72701, USA Corresponding author: Shahidul Islam, PhD, Professor Department of Agriculture, 1200 North University Drive, Mail Slot 4913, University of Arkansas at Pine Bluff, Pine Bluff, AR 71601, USA Submission date: 31 January 2010, Acceptance date: 17 February 2011, Publication date: 17 February 2011 Abstract Background: Bitter Melon (Momordica charantia L) is one of the most popular cooked vegetables in many Asian countries. Its experimental use in mice has indicated improvement in glucose tolerance against Type II diabetes and reduction in blood cholesterol. However, it has not been proven which alkaloids, polypeptides, or their combinations in the Bitter Melon extract are responsible for the medicinal effects. Green and white varieties of Bitter Melon differ strikingly in their bitter tastes, green being much more bitter than white. It is not yet known whether they are different in their special nutritional and hypoglycemic properties. Nutritional qualities of Bitter Melons such as protein, amino acids, minerals, and polyphenolics contents were determined using four selected varieties such as Indian Green [IG], Indian White [IW], Chinese Green [CG], and Chinese White [CW] grown at the University of Arkansas at Pine Bluff [UAPB] Agricultural Research Center. Results indicated that protein levels of IW were significantly higher than IG in both flesh and seed. Methods: Four Bitter Melon varieties, Indian Green [IG], Indian White [IW], Chinese Green [CG] and Chinese White [CW] were used for phytochemical analyses to determine protein contents, protein hydrolysis, amino acids contents, and their antioxidant and antimutagenic activities. All analyses were conducted following standard methods. Statistical analyses were Functional Foods in Heals and Disease: 2:61-74 Page 62 of 74 conducted using JMP 5 software package [SAS]. The Tukey’s HSD procedure was used for the significance of differences at the 5% level. Results: Moisture contents across the four varieties of Bitter Melon flesh ranged between 92.4 and 93.5%, and that of seed ranged between 53.3 and 75.9%. Protein contents of the flesh were highest in IW [9.8%] and lowest in CG [8.4%]. Seed protein contents were the highest in IW [31.3%] and lowest in IG [27.0%]. Overall, white varieties had higher protein contents than the green varieties. Compared with soy protein, most of the essential amino acid contents of Bitter Melon were similar as in soy proteins. Some amino acids such as Alanine, Glycine, and Valanine were relatively higher in Bitter Melon flesh than in soy protein. Phenolics contents of the flesh, seed, and seed coat tissue [SCT] were significantly different [p<0.05] among the four varieties. The four varieties were similar in their antioxidant activities of the flesh tissues; however, they were significantly different in their antioxidant activities in the seed and seed coat tissues [SCT]. Bitter melon varieties IW and CG, tested for antimutagenic effects, both flesh and seed had considerably high activities against benzo[a]pyrene with Salmonella TA98 [92-100% inhibition] and Salmonella TA100 [79-86% inhibition]. Conclusion: Based on these studies, Bitter Melon is a good source of phenolic compounds. All four varieties tested showed considerably high antioxidant and antimutagenic activities. Therefore, these natural plant phenolics can be a good source of biologically active compounds that may be applied in many food systems to enhance food values and special nutritional qualities. Further studies will be needed using more genetically diverse varieties to pin point the bioactive and functional compounds and their physiological properties. Key words: Momordica charantia, protein, polyphenolics, antioxidant, antimutagenicity Background Nutrition-related health problems such as hypertension, diabetes, ageing, obesity, arthritis, and cardiovascular diseases are prevalent among disadvantaged rural and urban populations, especially minorities in the Lower Mississippi Delta Region [1, 2]. Food consumption habits, dietary intakes, and meal preparation methods are believed to contribute to these problems. Dietary intervention through the consumption of specialty foods may alleviate the nutrition related disorders. In addition to the commonly used native herbs and vegetables in the US, many exotic herbs and vegetables are known for their special nutritional and medicinal properties [5]. During the past decade or two, Americans have realized that they could control their own health problems and reduce risks of many chronic illnesses by changing certain dietary behaviors [6]. The popular belief of Bitter Melons to improve glucose tolerance in Type II diabetes and lower the blood cholesterol. However, it has not been ascertained if or which alkaloids, polypeptides, or combination of these chemicals, are responsible for the medicinal effect. Functional Foods in Heals and Disease: 2:61-74 Page 63 of 74 Certain vegetables contain an abundance of polyphenolics, terpenoids, isoflavones, anthocyanins, amino acids, minerals, vitamins, and other antioxidants that are associated with protection from cancer, cardiovascular diseases, diabetes and hypertension [4, 7-12]. The most popular and useful group of the vegetables belong to the family Cucurbitaceae [13]. One of the members of this family is Bitter Melon [Momordica charantia L.], also known as Karela or balsam pear, an annual fruity vegetable. It is a delicacy for the East and Southeast Asian people, especially the people of India, China, Japan, Taiwan, Bangladesh, Pakistan, Thailand, Malaysia, Indonesia, Philippines, Nepal, Bhutan and Sri Lanka. Bitter Melon is also a popular vegetable in the West Indies, Brazil, Colombia, Cuba, Mexico, Panama, Peru, and some European countries. The bitter taste, for which the fruit is named, is perhaps due to the alkaloid momordicine, sometimes generalized as cucurbitacine. The green warty fruits of this plant are used as a vegetable, rich in vitamin A, vitamin C, and iron [14]. Fruits vary in size [1.0”- 9.8” long and 1.0 - 5.9” wide]. Fruits may be of oval, round, oblong, club, etc., in shape. Fruit colors at harvest vary from dark green to creamy white. Fruits mature in 45 to 80 days and turn red when ripe. The fruits, leaves, and roots of Bitter Melon are traditionally believed to have medicinal value in reducing blood sugar levels for diabetic patients [15, 16]. The various medicinal properties of bitter melon are well known in eastern Asia [17]. Sofowora [18] reported several uses of M. charantia in traditional medicines in Africa. Pharmacologically, the hypoglycemic properties of the plant organs were established by Lotlikar et al. [19]. The polypeptides from the seeds and fruits of M. charantia were considered as antidiabetic agents [20-24]. Cucurbitacines isolated from several species of the family Cucurbitaceae showed antitumor effects [25-27]. Lin et al. [28] isolated two lectins from seeds of M. charantia, momordin and agglutinin, showing momordin to inhibit protein synthesis by Ehrlich Ascites cells. Licastro et al. [29] announced that two proteins isolated from the seeds of M. charantia inhibited protein synthesis and subsequent DNA synthesis in normal and leukaemic human peripheral blood lymphocytes. Spreafico et al. [30] reported a protein inhibitor from M. charantia showing immunomodulatory activity in mice. Bitter Melons are used as cooked vegetables by the ethnic people from Asia, Africa and Europe, but American consumers have not yet developed a taste and appreciation for it. The crop could be introduced in the US as an additional food source possessing special nutritional properties. Therefore the functional compounds contained in these foods and their medicinal effect demand for thorough investigation followed by precise clinical studies. Research is also required for developing suitable varieties of this vegetable for their production potential and specific nutritional and medicinal qualities. In our studies during the past seven years, we have established that Bitter Melons can be successfully produced in Arkansas and the southern states. Also, we have some data generated on the recipes and their acceptability to the local consumers. Methods Four selected varieties of Bitter Melon were tested in randomized complete block Functional Foods in Heals and Disease: 2:61-74 Page 64 of 74 design with four replications on Calloway silt loam soil at the UAPB Agricultural Research Center. Plants were grown on upright trellises with 10 ft. between rows and 12 ft. within rows. Two four-week old seedlings were transplanted in each hole at the trellises. N, P, and K fertilizers were applied pre-plant, using 200 lbs per acre of 13-13-13. Irrigation was provided by drip irrigation system. Weeds were controlled by covering the beds with black plastic. Roundup [Glyphosate] was used in controlling weeds around the beds and allies. Melons were harvested twice a week beginning mid-June and ending